Date: Mon, 02 Jul 2007 14:13:40 +0200 From: cpghost <cpghost@cordula.ws> To: Ian Smith <smithi@nimnet.asn.au> Cc: freebsd-questions@freebsd.org Subject: Re: kern.hz="100" stops high-pitched whine Message-ID: <4688EBF4.8040409@cordula.ws> In-Reply-To: <Pine.BSF.3.96.1070701234407.12944G-100000@gaia.nimnet.asn.au> References: <Pine.BSF.3.96.1070701234407.12944G-100000@gaia.nimnet.asn.au>
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Ian Smith wrote: > On Sun, 01 Jul 2007 13:12:28 +0200 cpghost <cpghost@cordula.ws> wrote: > > > I'm using fan-less Soekris (266 MHz) and EPIA (500 MHz) > > boards with -STABLE. Those boards have been emitting a > > very high pitched annoying whine, similar to a dog > > whistle. Not everyone I asked could hear it, but I was, > > and it was driving me crazy for months. > > > > This whine stopped entirely the moment I put > > kern.hz="100" in /boot/loader.conf and rebooted. > > Quite relieving! > > Possibly a beat frequency between the 1kHz default slicing and some > faster oscillator on board? You could play around with kern.clockrate, > sometimes quite small frequency changes make a difference, especially if > it's a harmonic. Default HZ jumped from 100 to 1000 probably around the > time when more servers were seen running at nearer 3000MHz than 300 :) > Interesting! I've booted the EPIA with Hz=840 and Hz=1160, and the whine was *considerably* quieter in both cases. It really seemed to be some kind of harmonic oscillation at Hz=1000. Now I'm back to HZ=100, which seems to be ideal. > > Are there any reasons NOT changing kern.hz from the > > default 1000 back to 100? With my typical mix of > > desktop apps (EPIA) and networking / server (Soekris), > > everything seems to be running just as smoothly with > > 100 Hz than with 1000 Hz (testing now for two weeks > > without problems). Even playing videos with mplayer > > on the EPIA doesn't look different in any way. > > No problem then, and a lighter interrupt load; probably enough to notice > in top. If you want to run dummynet or something else? wanting quicker > ticking you could try HZ=200 - 500. 200Hz on my Celeron 300 works well. > > > Is it okay to stay with 100 Hz with this type of > > low-speed CPU/boards? Or are there some compelling > > reasons not to? > > If it's happy, smooth and keeping up, it's fine. > > Cheers, Ian > I'll stay with 100 Hz for now. Should I need dummynet, I'll crank it up slowly. Thanks, -cpghost. -- Cordula's Web. http://www.cordula.ws/
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